Net Capital Requirements - Additional Information (Details) $ in Millions |
Dec. 31, 2019
USD ($)
|
Dec. 31, 2018
USD ($)
|
|---|---|---|
| Regulatory Capital Requirements [Abstract] | ||
| Net capital | $ 2.0 | $ 2.3 |
| Excess net capital | 1.8 | 2.1 |
| Minimum net capital requirement | $ 0.2 | $ 0.2 |
| Ratio of aggregated indebtedness to net capital | 1.26 | 1.14 |